The BSA A7-A10 Forum

This is more a information topic which may help some in trying to decide what brand of pistons to buy when needed.

I bought a pair of pistons from British Only Austria, mainly because the current exchange rate makes the OZ dollar strong against the Euro. They cost me Aus $150 (104 Euro) landed in Oz.

The pistons are Taiwanese, Fuh Juinn brand. They are 7.25 - 1 (flat top). As you can imagine I was very reluctant to buy these due to the poor reputation of a lot of Eastern products but they assured me the quality was good and they have sold lots without problems.

I am very happy with them. They are a cast piston and very well machined. They have a .005" grind (ovality) which is the same as a Hepolite. The thing that I hope does give them a advantage is their weight, they weigh the same as a Hepolite. This is one area that can be a problem with GPM and JP pistons, they are usually quite a bit heavier than originals. I have given them .004" clearance in the bores.

Time will tell how they will wear and perform when hot etc but they look good and I am confident they will be ok. I guess the thing is dont dismiss eastern made stuff without checking it out first.

Title: Re: Eastern pistons
Post by: cus on 23.04. 2010 05:09

G'day Brian,I have a good contact in Vic. that sets your pistons up with a 3 peice oil ring,he did my pistons,...great job, let me know if you're interested,

Cus

Title: Re: Eastern pistons
Post by: muskrat on 23.04. 2010 18:39

G'day Brian, will be interested to see how they perform. Weight is important as is the ovality.Do cast pistons expand more or less than forged ? I thought 4 thou is a bit much.Was it you that spoke of the Total Seal gapless second ring ? I'd like to try that.Shame the pistons had such a long journey Taiwan/Austria/Australia. if we could get them direct it would shave another $50 off the price.Do you know if anyone does forged pistons for our bikes anymore ?Cheers

Title: Re: Eastern pistons
Post by: MG on 23.04. 2010 18:56

Hello to all!

I also would like to hear how they perform. Let us know!

muskrat,cast pistons expand slightly less than the forging alloys, but the latter offer higher material strength and therefore are better suited for high power/high temp. applications.4 thou imho is okay, that's what JP recommends too.Ref the long journey of the parts: If everything was sold to you guys down there directly, BOA would soon be broke and I'd loose my local supplier. So just keep ordering here, PLEASE!!! *lol* *contract*

Cheers, Markus

Title: Re: Eastern pistons
Post by: muskrat on 23.04. 2010 20:31

G'day Marcus, No worries mate. Just had a look at their site and bookmarked it. Very good.Good suppliers of BSA stuff down here are few and far between. I often think how lucky you lot in Europe are with the number of suppliers.Cheers

Title: Re: Eastern pistons
Post by: Brian on 23.04. 2010 22:51

G'Day Muskrat, I always give my pistons .004" clearance. BSA recommends .003"-.0045" for solid skirt A10 pistons. I dont run my engines in carefully like some so like the clearance to be adequate.

I doubt that you would find forged pistons anywhere for BSA's, or most other makes even. As for rings I just use the standard rings, I've never bothered with any of the alternatives and havent had any problems yet. As Cus suggests you can get the three piece oil rings. I have always believed that a well assembled standard engine will do everything that is asked of it.

I have not long discovered British Only in Austria and the pistons are the first thing I have bought although I have just ordered a set of cam followers from them. So far I cant fault them, everything on their site is priced so no nasty surprises and its easy to order from them. They use paypal so payment is easy. While the exchange rate stays good I will probably get more stuff from them. Like you say reliable suppliers of stuff for our bikes are hard to find.

Title: Re: Eastern pistons
Post by: muskrat on 24.04. 2010 06:13

Thanks Brian, Yes I just had a good look at their site and will be ordering a few bits. just bent an inlet valve !!!I used to give my race motors 4 1/2 thou but did 3 on the cafe. Run in, wots that ? 500 miles tops. LOL.I have a set of forged 10.5:1 in at moment and another +20 set as spares. JB brand from the US with an offset pin, but haven't been able to find any more.You are right in that a std motor is good for what they are made for but I tend to ride a little harder than most classic riders and tend to soop up anything I get my hands on (even this old nerd box). I know most will say I'm a fool, but I have fun.Oh, beer o'clockCheers

Title: Re: Eastern pistons
Post by: MG on 24.04. 2010 08:32

Brian,

I mentioned that several times on the forum already, but once again especially for you: *smile*Forged Wiseco pistons for the A10 in 9:1 are available from Cake Street Classics (CEO Roger Shirman) in the UK. Great stuff!

Cheers, Markus

Title: Re: Eastern pistons
Post by: Brian on 24.04. 2010 08:42

Thanks Markus, I will keep that in mind. I cant see myself using 9-1 though, I use 7.25-1 in all my engines except my 61' Flash which has 8-1 in it.9-1 would be good if you were chasing performance but I have found 7.25-1 with a 356 cam gives a very nice engine. Nice and smooth and tractable but still with good performance.I suppose living in Austria you are able to visit BOA and peruse their goods, lucky devil !

Title: Re: Eastern pistons
Post by: MG on 24.04. 2010 11:22

Quote

I suppose living in Austria you are able to visit BOA and peruse their goods, lucky devil !

Yep ;D

Title: Re: Eastern pistons
Post by: A10Boy on 27.04. 2010 11:37

With the quality of modern "petrol" 7.25 is plenty high enough, especially with an iron headed engine.

Title: Re: Eastern pistons
Post by: Brian on 28.04. 2010 05:08

I fitted the pistons today and discovered one problem, the rings. They had way too much end gap, .020". I had a set of Hepolite rings so I used them. Now I have a spare set for a STD or +.010" engine. Otherwise it all looks good.

Title: Re: Eastern pistons
Post by: muskrat on 28.04. 2010 09:46

Lucky you had spares mate. Having to wait for rings would be a bugga. Why is quality so hard to get with parts made elsewhere (China, Taiwan, India etc) ? Lucky it was the rings and not the slugs that were wrong.Cheers

Title: Re: Eastern pistons
Post by: Brian on 28.04. 2010 09:53

I try to keep a few spares that might be needed.

I'm not sure if the rings are made with too much gap or maybe the wrong ones were put in with the pistons.

The pistons look good and the pins are the correct size etc so maybe they did put the wrong rings in the boxes.

Title: Re: Eastern pistons
Post by: muskrat on 28.04. 2010 10:04

Could be the case. When I bought two sets of pistons from US, one set had no clips, the other no pins.Cheers

Title: Re: Eastern pistons
Post by: MG on 16.07. 2010 21:05

Brian,anything worth reporting about the pistons already?

Title: Re: Eastern pistons
Post by: Brian on 16.07. 2010 23:27

They are in the engine Markus but I probably wont have this one finished for at least 6 months. Its another plunger A10 I'm building.

While we are on the subject of pistons, a friend recently bought a pair of GPM's for his A10 so we weighed them bare, exactly the same as a set of genuine BSA ones. There seems to be a lot of different opinion of GPM pistons, I havent used any in a A but I have used them in B series BSA's without any problem. I had a good look at them and we measured the ovality etc and I would have to say it all looked good.

Title: Re: Eastern pistons
Post by: chaterlea25 on 16.07. 2010 23:47

Hi All,Brian,I had the same problem withe the ring gaps on the set I fitted recentlygaps were 25-30 thou???Had to wait a week or more for a replacement set!!

RegardsJohn O R

Title: Re: Eastern pistons
Post by: a10gf on 17.07. 2010 00:11

Totally off topic comment, sorry:

Brian, I admired the very good quality of your 003 photo above, and the exif info identified it as an old canon A410 (http://www.dpreview.com/reviews/specs/Canon/canon_a410.asp). Good to see one does not need the latest megagigabyte cam to get great photos. And great looking engine btw

Title: Re: Eastern pistons
Post by: Brian on 17.07. 2010 02:26

I got rid of the old HP Erling and have been using the other halfs A410, I still havent bought another camera, I'll get round to it oneday. (like a lot of other things)

Title: Re: Eastern pistons
Post by: MG on 17.07. 2010 07:37

Brian, thanks for the update.I'll ask again in 7-8months, okay? *smile*

Title: Re: Eastern pistons
Post by: olev on 20.07. 2010 13:08

Gday,I've got hold of a set of 40 thou o/s pistons for the A7.They seem to be about 8:1 CR.The numbers on the packet say 67/1446 (Made in England)The numbers on the piston say '67/1447 BSA' '1mm OS'then G over 46 inside a circle.The closest match is Bacon's book which lists a 67/1442 as an 8:1 for 1958 - 1962.They are solid skirt and weigh 7 gm more than the 7.25:1 originals.Any thoughts on what I've got here? genuine BSA?and why do they have oil holes into the gudgeon bushes if the pin isn't supposed to turn in the piston?cheers

Title: Re: Eastern pistons
Post by: Brian on 20.07. 2010 13:24

67-1446 is the part number and 67-1447 is the casting number. 67-1446 is correct for a 1mm or +.040" oversize 8-1 piston.

As for the brand, what was on the boxes? JP and GPM and the pistons I bought all come in clearly marked packets with the brand name on them.

I am not sure what pistons are made in the UK if thats whats on the packets. Hepolite come in distinctive boxes. All the genuine BSA pistons I have come across have the piled arms stamped into the top.

The gudgeon bushes have oil holes to let the oil in as the pins turn in the bushes.

Maybe you could post a photo of the packets the pistons came in and someone may recognise them.

Title: Re: Eastern pistons
Post by: MG on 20.07. 2010 13:29

Hepolites woud be split skirt, so are JPs.The GPMs are solid skirt, and as far as I can remember they're marked with metric o/size values.

Title: Re: Eastern pistons
Post by: KiwiGF on 18.08. 2011 09:13

Hello Brian I have just got std size flat top pistons from British only Austria and wondering how I can tell who made them as there are no manufacturing markings etc they look the same as yours And were circa 170nzd delivered

I got a few other prices for JP pistons NOS hepolites etc (all more than double the cost) but taking everything into account these pistons seemed the best bet being new lowish compression and lightweight

Title: Re: Eastern pistons
Post by: KiwiGF on 18.08. 2011 10:02

Hello Brian a quick check revealed the BOA gudgeons are 003 underside of 0.75 and the rings all have a 022 gap which will increase to over 025 when the barrel is honed to suit the pistons the max gap i think is 013

I just wondered if I am unlucky and BOA have sent the wrong parts or if your parts are the same

The pins fit Far too easily into the pistons w/o warming them up and are also loose in my billet rods :-(

Title: Re: Eastern pistons
Post by: BSA_54A10 on 18.08. 2011 10:52

Quote

I fitted the pistons today and discovered one problem, the rings. They had way too much end gap, .020". I had a set of Hepolite rings so I used them. Now I have a spare set for a STD or +.010" engine. Otherwise it all looks good.

No you do not have a spare set of + 20 rings.It is a common fallacy that you can grind down a set of oversized rings to fit a smaller bore.You can't.The curvature will be wrong and the rings will apply very uneven pressure on the cylinder wall causing rapid oval wear of the bore.You might get away with it in an emergency, like to get the bike back on the road fro the BSA National Rally ( cheesy plug ) but you should replace them with the correct size as soon as you get home.

Title: Re: Eastern pistons
Post by: Brian on 18.08. 2011 10:57

When I bought mine the pins were the correct size but the rings had way too much end gap, I cant remember exactly what the end gap was but it was at least .020" or more, I didnt use the rings but fitted a Hepolite set I had.

If your pins are loose in the rods dont use them. When you say billet rods I take it they have no gudgeon bush, the pins run directly in the rod. Do you have a set of original pins that fit the rod correctly, if you do heat a piston and see if the pin will push in. If it does you could use the pistons with different rings and pins. This of course means you would have to buy new pins and rings which probably makes the whole thing more expensive, alternatively you could send them back.

The ones I put in my engine have done just on 1,000 miles now and so far so good. It seems like they will run ok but time will tell what the wear will be like. I have a set of Hepolites ready to put in if these ones cause any trouble.

Title: Re: Eastern pistons
Post by: KiwiGF on 18.08. 2011 12:09

Hi Brian thanks for that I have some barely used pins and I could use them as they fit fine but I think I have the time to get BOA to replace the Pins and rings I'll post the results of that here......

I was going to buy pistons from JP but on this forum posters said JP rings were rubbish... so i don't feel so bad about the BOA rings being wrong I was sort of expecting it.

Apart from comments JP pistons were heavy and the rings rubbish the final straw was that it was cheaper to buy JP pistons from UK distributors like "red lizard" than direct from JP and even when I pointed that out to JP they refused to budge on price. JP also wanted twice the $ to ship from Aus to NZ than UK suppliers charge to ship to NZ!

I bought the SJ billet rods from thunder engineering Of the UK $550 nzd delivered and they supply SRM so I guess they are the SRM rods but cheaper also they arrived in NZ within a week and look great and yes there is no bush in the small end the only downside of these rods is the barrel cut outs will need to be widened by about 6mm as they are wider than OEM rods

I am not sure whether to simply take a grinder to the barrels or get the honer company to do it with a mill a slight concern with doing this widening is that the barrels have liners

Title: Re: Eastern pistons
Post by: KiwiGF on 31.08. 2011 11:55

After a couple of weeks of waiting British Only Austria could not get a reply from the makers of the pistons (alledgedly a Taiwanese outfit) and they have asked me to return the piston as a set as they cannot replace just the faulty rings and gudgeon pins.

In addition they reckon they cannot "meet my requirements for this price"

My requirements being usable rings and gudgeon pins!

Pretty poor of British Only I reckon. I cannot recommend buying this type of piston set from them based on this experience

Title: Re: Eastern pistons
Post by: terryk on 01.09. 2011 04:27

Does anyone know how much weight difference there is between JP pistons and hepolite?

Title: Re: Eastern pistons
Post by: KiwiGF on 01.09. 2011 07:53

I asked JP and they gave the weight of their A10 std bore pistons as 351grams for the 6.5:1 and 343grams for the 7.25:1

I have quite a collection of hepolites and non branded pistons and the hepolites are the heaviest and much heavier than the BOA pistons mentioned above (using balance on ruler on nail method)

I have no way of measuring the weight in grams of the hepolites though - sorry

Hi Terry- firstly BOA refunded me for the duff piston sets I got from them and also refunded me all the freight involved so good on them!

After quite a few quotes including very high prices for NOS hepolites I bought JP pistons from Draganfly- odd it's cheaper to have them sent from aus to the uk and then back to nz! Draganfly had nil stock so I had to wait for them to do all the traveling.

Anyway using a metal ruler and nail as a balance I can tell you the JP pistons std bore flat tops part no 0652 are slightly lighter than the hepolite pistons listed below. Interestingly I found the difference about equal to the difference between a gudgeon pin with a straight bore as supplied by JP and some tapered bore pins I had.

I hope this info is of some use- I was surprised the Hepolites were heavier than JP as I've been told the Hepolites are direct equivalent to the OEM BSA pistons, and also I've been told that a general problem with JP's is that they are much heavier than almost any other brand, but that does not seem to be true in the case of A10 pistons

11062 +06011412 +02011787 +060Chinese? std

Title: Re: Eastern pistons
Post by: BSA_54A10 on 01.12. 2011 13:15

Quote

Apart from comments JP pistons were heavy and the rings rubbish the final straw was that it was cheaper to buy JP pistons from UK distributors like "red lizard" than direct from JP and even when I pointed that out to JP they refused to budge on price. JP also wanted twice the $ to ship from Aus to NZ than UK suppliers charge to ship to NZ!

Australia Post is now just about the most expensive O/S postal system in the world so do not blame JP for that, Julia Gillard yes, JP no.As for unbranded pistons I never even think of using them.If a product is good then the maker will want to tell the world about it, if it garbage they won't.If a supplier sells quality pistons then they will sell them in branded boxes so the world will know that they sell good quality pistons.If neither want their name to be associated with the pistons it is most likely because they want you to forget where you got them from before they failed & totaled your engine

Title: Re: Eastern pistons
Post by: chaterlea25 on 02.12. 2011 10:21

Hi All,Just as an addendum to this thread the previously "no name " pistons are now "branded" Hepolite *eek* *eek* *eek*and sold/distributed by Wassels,HTHJohn O R